case 比較対象フィールド when 比較値1 then 代替値1
                        [when 比較値2 then 代替値2]
                        .....
                        [else デフォルト値]
end

select 
case 3 when 3 then 'three'
       when 4 then 'four'
end as case
from   dual;

    case
--------
   three

select 
case 5 when 3 then 'three'
       when 4 then 'four'
       else 'none'
end as case
from   dual;

case
----
none

select 
case 5 when 3 then 'three'
       when 4 then 'four'
end as case
from   dual;

case
----
null

SELECT *
FROM TABLE
WHERE 
(CASE WHEN FLG = '1' THEN HINBAN
      WHEN FLG = '0' THEN HEN_HINBAN
 END
) LIKE 'SB_%'